Semester

Fall

Date of Graduation

2021

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Terence Musho

Committee Member

Christina Wildfire

Committee Member

Edward Sabolsky

Abstract

Recent experimental demonstration of new reaction windows for coal char/methane reactions that are less energy-intensive, provides innovation for modular reactors. However, the correlation of the exact mechanism for the enhancement of these reaction windows is not certain. This study investigates the simplification of these experimental studies by developing a well-characterized coal char simulant. The approach involves using a computational approach to screen macroscopic composition to replicate the dielectric and compositional response of actual char. This study is focused on PRB coal char. A discrete element method (DEM) technique was used to simulate the packing of coal chars to give the precise distribution of particle sizes. Micro-CT images of actual coal char were taken and the Feret diameter and particle count were used in DEM simulation. Using the packed DEM geometry, a finite element analysis (FEA) using COMSOL was utilized to solve Maxwell’s equations to match the experimental dielectric properties. Once the required volume fraction and constituents were known, the coal char simulate was synthesized. The comparison of simulation dielectric and actual char dielectric was within 5\% error. The synthetic char was experimentally synthesized and the density of the synthetic dielectric was determined to be 0.5 g/cc and the actual char had a density of 0.4 g/cc. It was determined that the imaginary part of the synthetic char was much larger than the actual char. This was reasoned to be due to the larger electrical conductivity associated with the synthetic char material. Further investigation of the actual char through both optical and scanning tunneling microscopy revealed significant amount of ash content surrounding the char. It is hypothesized that this ash layer coating the char as a result of pyrolysis process is leading to decreased electrical conductivity. A similar FEA approach was used to investigate the particle morphology of a magnetite (Fe$_{3}$O$_{4}$) catalyst embedding on a coal char substrate to understand the localized temperature and electric field enhancements. It was determined that a particle shape significantly influences electric field and localized temperatures. In the absence of the shaped particle the peak electric field strength and subsequently, the volumetric heat flux was two orders of magnitude lower. An optimal geometry and volume fraction to enhance these localized field effects were found during the study.

Comments

The page numbers appear to be fixed on my Adobe Acrobat. Hopefully this issue is corrected.

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